Mismatch encode decode

[forayr]

Regression starting from f4d113c1 (JVET-N0349: decoding parameter set (DPS)).
Vtm crash when decoding some streams.
For example:

git clone ​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM.git vtm
git checkout f4d113c1
mkdir vtm/build && cd vtm/build && cmake .. && make -j8 && cd ../bin
./EncoderAppStatic --SourceWidth=56 --SourceHeight=48 --InputChromaFormat=420 --InputBitDepth=10 --Profile=next --FrameRate=60 --FramesToBeEncoded=1 --GOPSize=4 '--Frame1=B 1 5 -6.5 0.2590 0 0 1.0 0 0 0 4 4 -1 -5 -9 -13 0' '--Frame2=B 2 4 -6.5 0.2590 0 0 1.0 0 0 0 4 4 -1 -2 -6 -10 1 -1 5 1 1 1 0 1' '--Frame3=B 3 5 -6.5 0.2590 0 0 1.0 0 0 0 4 4 -1 -3 -7 -11 1 -1 5 0 1 1 1 1' '--Frame4=B 4 1  0.0 0.0    0 0 1.0 0 0 0 4 4 -1 -4 -8 -12 1 -1 5 0 1 1 1 1' --FastSearch=1 --LumaLevelToDeltaQPMode=0 --MaxCUWidth=16 --MaxCUHeight=24 -i source.yuv -b stream.vvc
./DecoderAppStatic -b stream.vvc

VVCSoftware: VTM Decoder Version 5.0 [Linux][GCC 8.3.0][64 bit] [SIMD=AVX2]
terminate called after throwing an instance of 'Exception'

what():

ERROR: In function "read" in ../../../../../vtm/source/Lib/CommonLib/BitStream.cpp:293: Exceeded FIFO size

[ksuehring]

It's actually a specification bug:

After adding sps_video_parameter_set_id to the SPS, in this configuration the first two bytes of the SPS are equal to zero.

The second byte of the the NAL unit header is defined as:

	nuh_layer_id              u(7)
	nuh_reserved_zero_bit     u(1)

So with nuh_layer_id equal to zero, this is the third zero byte in a row, which leads to a start code emulation, because the NAL unit header is not included in the start code emulation prevention.

We usually avoid such start code emulations by not allowing the last NAL unit header byte to be equal to zero.

In this case, it could easily be achieved by changing nuh_reserved_zero_bit to nuh_reserved_one_bit

But since there is a intention to give this bit a meaning later, it may make more sense to increase nuh_layer_id, i.e. nuh_layer_id_plus1

[ksuehring]

I submitted MR 559 with the suggested nuh_layer_id_plus1solution

​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/merge_requests/559

[bbross]

Fixed in D5 v8